FAQ

Here you’ll find the answers to our most frequently asked questions. If your question isn’t answered here, or on our technical pages, you can contact us directly.

What about air traffic when people start flying instead of driving?

What air traffic? We don’t even need to invoke smartplane ™ technology to address this concern, but we can add it to the discussion later.

Most people form their ideas about this topic without small aircraft experience, or with it in a very urban context ,or perhaps from a bit of sci-fi movie magic. But by the time a few thousand small aircraft start to slowly repopulate empty airfields one at a time, our perspective will have profoundly shifted away from sprawling airports that concentrate people and airplanes for “convenience.” Modern flight will expand our habitat exponentially, diluting the urban requirement.

Think about it: passengers from all over a five-million-acre region are first funneled to these packing centers, screened and made to wait, so that they can distribute from another such site upon landing into another five million acres of potential actual destination. Why not just come and go directly, to and from wherever? A modern jetport hallway is bigger than a Synergy landing site, and can be (or already is) located anywhere.

Taking people directly to and from their closest airfields in a car-like modern airplane makes older concepts of “traffic” utterly disappear. It can be hard to see this at first because the confining 2-D ribbons of congestion on the ground paint a greatly distorted picture in our minds. Pilots escaping the traffic prison marvel at the truth, which is that one can fly all day yet never even see the occasional fellow aviator pointed out on his screen, many miles away. It’s a freedom we dare you to think about, for the good of humanity.

Try this, the next time you’re stuck in traffic wanting your own Synergy: imagine leveling every obstacle, bump, and building for a thousand miles in every direction. Now imagine it all paved as smooth as a tennis court, and give yourself permission to drive anywhere you want on it, avoiding anything that looks scary. Now imagine stacking each empty three-million-square-mile-patio you just made, like a parking garage five miles tall. Now…put every car and truck in sight on a different level…and think about how quickly they’d make room for each other anyway, when not confined to a 12-foot wide lane. That’s the networked smart sky, AFTER companies make 100,000 airplanes a year for a thousand years, thereby finally catching up with auto numbers today.

Or, just go outside, look up, and count every airplane you’d consider a collision threat for the next five minutes. How many planes did you see traveling the crowded jetways on your last commercial flight?

Simulation studies reveal that even uncontrolled air traffic isn’t a problem until you try to concentrate everyone at a giant airport. The millions of empty cubic miles of airspace around us will stay that way. Coruscant will never happen, it’s physically impossible. The earth is far too huge.

Yet our tech industries today are thrilled to provide a proven, pocket-sized solution that could easily handle even that hypothetical level of traffic. Comparatively speaking, autonomous airplanes are a cakewalk compared to self-driving cars. We’ve had fully capable autopilots for decades. Synergy is working with a number of advanced initiatives for future on-board systems that will make operating your own smartplane ™ the most relaxing transportation experience you’ve ever had.

 

How can I put myself down to get one of these?

Although it’s by far our #1 FAQ, unfortunately, you can’t. This is a project determined to succeed, and taking orders for high-demand airplanes ahead of churning them out by the hundreds is historically just slow financial suicide.

It’s not about making one, or twenty, or two hundred. It’s about making enough of them, which means knowing what that number is, designing production accordingly, then executing perfectly.

We have an extraordinary plan that eventually gets everyone who wants one a Synergy Prime smartplane, much sooner than if we told everybody what they wanted to hear. It’s a plan every bit as good as the airplane, but equally dependent on time and capital.  Our job therefore is to be ready on the business front, ahead of factorial demand created when Synergy flies. We are gathering the team and resources it will take to launch that effort now. Please spread the word.

One aspect of our plan is similar to how Tesla began, but it bears noting that Tesla Roadster buyers at least had a Billion other vehicles on the road, each providing for the same basic societal need. The core mission of ‘moving people quickly and economically’ could be met with many options. For Synergy buyers, however, there is no such thing as time-efficient, on-demand, point-to-point, affordable group transportation for small groups of people. It doesn’t exist yet… but a billion people want it to.

Why do the tails push down, instead of lift?

If the horizontal tails were wings to make lift, Synergy would be like any other box wing, a configuration showing very little value over the many decades it has been tested. Besides those real shortcomings, though, the answer is that doing the opposite of a box wing turns out to provide dramatically superior results if done well.

1) Superior Stability in Pitch

2) Superior Stability in Yaw

3) Superior Turn Coordination

4) Enhanced ride quality

5) Increased laminar flow through interactivity (Constructive, not Destructive, biplane interference)

6) Increased aft margin

7) Instant lift at high alpha (note: tails unload during slow flight at high angles of attack)

8) Slower landing than cruise wing loading would normally permit, due to the above.

9) Corner drag eliminated

10) Dramatic structural advantage

11) All of the above by means of action against wake vortex; in other words, action against induced drag.

12) The highest possible span efficiency, far better than even a flying wing.

Bear in mind that for those familiar with the latest non-planar wing configuration studies, this is old news, but there are far more who don’t follow the details than those who do.

 

What differences do you expect between the model and the full scale?

Not a lot is different, except that bigger tends to fly much better. That is part of why it is so valuable to test smaller airplanes instead of larger ones, they amplify flaws.

As you shrink a full scale airplane down in size to make a model of it, things change really quickly. They get much worse! A full size plane that flies great in the real world may not even look accurately shaped by the time it is turned into a model, because to make it fly well small scale requires so many adaptations. Alternatively, as scale model builders can attest, a perfectly shrunken airplane often flies terribly!

The opposite is also true. The larger you make your scale model jet, for example, the better it tends to fly. However, also keep in mind that most successful scale models are much lighter than in scale proportion, to help compensate for the reduced air density and lower Reynolds number. They also fly proportionately 2x-3x faster than the real thing.

All of our Synergy scale models fly great already, without lots of power and despite their scale airfoils and heavy weights. They slow down well and are very stable and easy to fly. Modelers advanced enough to correctly build similar aircraft from scratch find that they are fun and forgiving. Maybe even a little boring compared to the typical RC insanity that’s possible at model sizes. They also learn that designing this aircraft is not easy to attack as a weekend project: even a ‘flat foamie’ model presents an engineering challenge.

So, with the above in mind, and of course many years of in-depth analysis, we expect the full size aircraft to be exactly what we want it to be. Most of that can easily be seen in model behaviors.

Interestingly, model builders tend to be more skeptical about the drag reduction initiatives this aircraft uses, and they get lost in what we’re saying. You see, at model airplane size, things like pressure thrust and active boundary layer control make NO DIFFERENCE whatsoever. The air is too thin, the speed is too slow… not by a little bit, but by huge multiples!

Fast model airplanes have a few obvious traits in common, like minimal fuselage size. At small sizes, a fast conventional model airplane is far faster than a scale Synergy, and modelers already know this without needing any proof. However, at mid-subsonic speeds, the air is more like water, or even wet concrete.

In fact, to get through it efficiently, conventional airplanes resort to blasting through as fast as possible, which is what the present opportunity space is all about. Aircraft designers today have a lot to learn about flying efficiently in the 200-400MPH range! It is a foreign realm they did not master, and the shapes we need are different than those that work at slower and higher speeds.

Lutz & Wagner, Stuttgart

Lutz & Wagner, Stuttgart

Synergy leads the way with the counterintuitive adaptations required to get the physics of this new frontier just right, and long after publication it will still be quite some time before ‘how it does what it does’ becomes common knowledge among experts in other domains.20071026_mc_squared_0041

It looks short coupled to me. I'm concerned about the stability.

Synergy is an amazingly stable aircraft.  For many that’s apparent when watching various models fly.  Pilots of our prototypes report that it’s like a sled on rails. But because people are more used to long-tail airplanes than the alternative physics that birds use for stability, the question comes up anyway. Synergy designer John McGinns has been granted two US Patents about creating drag reduction through increased stability and control. So let’s start from the beginning.

Yaw stability

Synergy has four vertical tail surfaces of generous size, all intentionally loaded (flying at an angle of attack) so as to actively stabilize the aircraft in all directions, even when flying straight ahead (less hunting or tail wagging). These also direct the airflow where it will cause a drag reduction. At the wingtips, the loading counters wake vortex. At the boom tubes, the loading fills the wake efficiently. The ‘vertical tail volume coefficient*’ that results is appropriate for a pusher. Stable! (A tractor prop is destabilizing, an aft prop is stabilizing.)

However, even the need for typical yaw stabilization is already greatly reduced. Because of the downloaded elevons at the wing tips and their effect on tip vortex, Synergy is like the ultimate implementation of the Bell Shaped Lift Distribution that makes the best flying wings. Negatively loaded wing tips bring difficulties for many designs, but having the BSLD negative load placed above and behind the tips- on a controlled airfoil- well that’s just nifty. Synergy is so stable in yaw it may not even need the vertical surfaces it has.

Pitch stability

When aircraft, such as hang gliders, have a swept wing planform like Synergy, many people recognize they’re already quite stable in pitch. Most don’t even need a tail. It all depends on the lift distribution, center of mass, and the pitching moment of the airfoils. Easy.

Straight wing airplanes, not so much. Their wings are not inherently stable about the pitch axis.

Ignoring the fuselage, then, Synergy might be regarded as a stable flying wing, in which we’ve added a very large pair of tails; flying them with an intentionally stabilizing download.

Its ‘horizontal tail volume coefficient*’ is quite conservative due to the large size and aft location of these horizontal control surfaces. (*Tail volume coefficients are numbers used to express the relative ‘aerodynamic leverage’ of a tail surface. They allow engineers to quickly compare apples to oranges among very different designs. Synergy ‘s numbers have plenty of company among noteworthy safe airplanes.)

An aeronautical design principle called decalage shows why some actually have it backwards: stability is increased in Synergy, decreased in a long-tail plane. Decalage is the difference between the angle of attack of the wing and the angle of attack of the tail. More decalage (more difference) equals more stable, less equals less stable. Synergy has more decalage.

Finally, in a long-tail airplane, the tail and the wing hit gusts at slightly different times, the delay causing the tail to amplify the resulting disturbance by inducing greater angle change. In Synergy, bumps are less amplified, and there is less ‘weathervaning’ due to crosswinds.

Prototype test pilots all agree, it’s “such a creampuff” that their only disappointment is not getting any bragging rights. One said, “I was expecting it to be more touchy, but it flies like a trainer.”

Ouch. So far, every form of analysis and testing says we have plenty of control to play with to dial it all in for our personal preferences.

Efficient Control and Stall Prevention in Advanced Configuration Aircraft, US 8657226

Aircraft Stability and Efficient Control Through Induced Drag Reduction, US 9545993

 

Dynamic stability depends upon a host of factors, each given equal attention, each adjustable to a degree. In the video below we stretch three seconds of flight into fifteen to illustrate the naturally damped convergent recovery due to the configuration alone. This behavior is confirmed in flight testing and other flight simulations.

 

 

Why don't you connect the upper surfaces together in the middle?

Connecting the aft horizontal surfaces by means of a horizontal connecting airfoil is an option described in John McGinnis’ ‘boxtail’ aircraft design patents. Many people imagine it would make things stronger and lighter, but it turns out differently.

It’s true that connected-box-wing designs are what people are more used to seeing, since ‘box wing’ and ‘tandem wing’ aircraft concepts have looked that way for more than forty years.

However, it’s worth noting that box wing designs have not become successful during that period. The ‘connector wing’ is, frankly, part of the reason for that. It causes more harm than good.

An airplane wing flexes up and down in turbulence, which can improve the ride and help achieve structural optimums. Making it stiffer requires ever stronger materials, which costs money or adds weight, or both.

Now when we attempt to brace a flexing wing, all the force that makes it flex in the first place is still there. Any bracing scheme just makes that force go somewhere else.

This is a very important concept to understand, because when one wing or tail is above or below another, using one to brace the other through rigid vertical supports (without diagonal connections) requires a corner connection that is very stiff and strong. This type of corner connection receives the ‘moment load’ we can visualize below, and it will fail under that load unless it is either extremely strong or extremely flexible. In the latter case, any bracing benefit from the connection is lost, and in the former case, the structures needed are excessively heavy in comparison to merely building the wing stronger in the first place.

In a boxwing design, much of the moment load normally only seen at the wing root also goes straight into the corners of the box at the wingtips. You can visualize this by removing the ends of a cardboard box to form a parallelogram  representing the left or right half of a boxwing aircraft. Look through the opening and visualize the upper and lower “wings”, “winglet” and “central plane of symmetry” while holding the central “fuselage side” of the box. Now, flex the “wingtips” up and down on the “winglet” side. The corners fold easily (and would have to, even if they were stiffer.)

Synergy has, instead, a double boxtail design that allows the wing to flex and for the loads to be distributed without excessive concentrations. The tail is naturally holding the wingtip down, while the wing is naturally holding the tail up (against the downward load of the tail) …but both can flex together with the wing. This creates a system in balance with itself and reduces connection weight in comparison to a centrally connected rear wing/tail.

 

Are you planning any sort of de-icing system on the aircraft in the future?

The short answer is yes, but we are not willing to go into much detail concerning which systems are being researched at this time. The basic idea is that many deicing schemes destroy laminar flow. That is an unacceptable result, because it is clear that many anti-icing schemes are compatible and complementary with laminar flow. Our strategies do not accept aerodynamic or safety compromises.

The longer answer, which may strike some as controversial, concerns why anti-icing in the future has a different priority than has been the case historically. Let’s be clear: any kind of scheduled air service or flight to a rigid time and place demands that an aircraft have ‘flight into known icing’ capability (FIKI). It’s always a good thing to have. However, while companies race to develop such commercially valuable aircraft, society’s broader adoption of affordable personal aircraft will be quietly moving the target. It will not be quite as important for the majority of future aircraft.

Air travel as it stands now is an out-of-control monster. Billions of dollars are spent on the sprawling ‘cities’ required not only to land and load our giant Air Busses, but to process the hordes who have to spend several hours getting to and through them, at times that are very inconvenient to start with. Yet extreme punctuality is key, or it just gets worse. For scheduled GA aircraft, which currently lack the speed, economy, and range to provide a financially sound alternative to the hub-and-spoke regional transportation system, FIKI is even more safety-crucial.

However, when people gain control of their travel options, as they have with their cars, they will not choose to fly in bad weather. When they are flying and discover it would be nice to take a potty break, grab some lunch, and take in a cultural experience somewhere off the beaten path, rather than proceed into worsening conditions, they have the option to do so because there are beautiful little airfields almost everywhere. For the majority of such uses, Synergy’s most basic level of ice protection will provide safety and peace of mind because its performance and range allow unscheduled travel to and from anywhere.

Is there a place to see progress on the full scale aircraft project?

Yes, John McGinnis and Team Synergy volunteers post updates several times per year on the Synergy Aircraft Facebook page. An album related to the build is here.

Have you done any 3-D CFD modeling?

Yes. A large number of tests have now been run using Large Eddy Simulation for the v.32 aircraft in both the powered and non-powered condition. The results of all tests are very exciting, and have confirmed our success in areas that are more difficult to validate using conventional methodologies. All expected performance capabilities appear to be well in hand, and basic qualities have long been well understood through unmanned developmental flight testing.

Synergy appears to show very little drag. What little there is occurs in areas we’ve designed to benefit from the use of power. Its beyond-the-textbook design principles have now been qualitatively AND quantitatively validated, and that approach was perhaps the most significant of our technical risks. (When we completed the design to the level required to start building it, the cost of this level of analysis was much greater than the cost to complete the first full size aircraft.) We have now reduced these capabilities and principles to a “next generation” algorithm for greatly enhanced conceptual and preliminary aircraft design.

We’ve also created such a powerful in-house resource… world class, in fact… that it IS possible to test all of the things aircraft designers dream about. We’re doing it, and can do it for anyone else, too. Details here.

Computational Fluid Dynamics software attempts to solve simplified forms of the equations of fluid dynamics, usually the Euler, Navier-Stokes and Barnette equations. Most CFD software has been refined to the point where a reasonable degree of accuracy can be obtained for well-known geometries and flow conditions. However we are excited to now be using an entirely new approach: no assumptions, just physics.

2613804ec8-synergy_bjet

Have you seen the new __________ from __________?

Probably. By the time most people see new developments in aviation, engines, or technology, those working inside the industry have known all about it for years. Of course, every once in a while something will stay truly secret for good reason, surprising everyone when it arrives.

We get a ton of emails from people watching the new developments closely, and we appreciate it. Naturally, most are late to the party, however, so this  FAQ will be updated from time to time with links to some of the other cool things going on out there while we’re busy.

It doesn’t mean we endorse it or agree with it, or even that we think it’s worth a look. There is a lot of stuff happening these days, and some of it needs commentary!

Can a company develop other airplanes like Synergy, or is it patented?

Sure.  Right now, Synergy Aircraft holds the opportunity to commercialize a specific family of the many patented BoxTail aircraft types. We’re also free, like any other company is free, to pursue license rights for other aircraft, such as business jets, UAVs, etc.  (Why should they?) A related technology for stability and control through induced drag reduction applies to more conventional wing and tail designs, as well.

Since any aircraft requires such a focused commitment to development, there is ample room for other companies to establish market category leadership through patent licensing, with or without category exclusivity (which is a possibility). Any company seeking to develop aircraft under license may contact the patent owner’s representative for a pain-free licensing experience.

Requests for aeronautical design and development under contract may be considered by us directly, or could be sourced through our partnerships with service providers.

How long before the prototype is completed?

We’ve completed and flown many prototypes, using the most proven method; one that tends to reveal and amplify any negative inherent traits. Sub-scale aircraft development is how virtually every aircraft is tested, because big planes are easier in terms of improving the basic character seen in smaller models (that are underpowered and overloaded compared to recreational R/C airplanes). This process has removed many technical obstacles, allowed development and testing of full scale systems like landing gear, speed brakes, and wing removal, and is now mostly complete.

As to John’s full scale aircraft, we don’t know yet. A huge amount of the work has been done, and what remains is well in hand. However, it is quite expensive. Our 2016 timeline was half funded by profitable operations, but the second half was not, nor has there been enough cash available for him to preserve the 2017 timeline. Assuming we raise ALL the capital required for our business plans, we’re presently less than a year from flight of his or other prototypes.

The Company has a bigger agenda and more options as we go forward. In fact, we will be making short-run molds from John’s parts before they are assembled, which is part of the reason they cannot be joined together for the sake of showing progress. A few Alpha prototypes will be built from those molds, and having worked all the details out, they will build fast. Completion of one or more of them could theoretically occur ahead of the original, then we will submit them to extensive testing and analysis.

Beta prototypes built from production-candidate tooling designs will be the first planes a member of the public could obtain, but we expect a bidding war until we go forward with a production timeline and product announcement. Our goal is to be the first aircraft company to deliver affordable aircraft in adequate quantity to meet demand, and we’ll share the details on how that can be achieved…sometime ahead of creating even more demand.

Don’t worry: No one will miss the news when Synergy is ready to go.

 

Will this aircraft be available as a kit?

Yes, Synergy is intended to become an incredibly easy-to-build kit aircraft in its earliest forms. Kit airplanes represent about half of the new aircraft completed each year (!) and they can be (and often are) a flying showcase of the most advanced technologies and safety features available. We will have a program to assist anyone to complete their aircraft in a Synergy build center, starting here with us.

kids2wks

The Glasair Sportsman is one of the leading fast-build kit airplanes.

Although newbie airplane companies sometimes rush off headlong into spending hundreds of millions of dollars, racing to certify processes and parts that aren’t even finalized, and shouldn’t be, it’s clear that the kit market provides the very best path to lower costs, lower risks, and a thoroughly refined product offering. By harvesting the collective brilliance of the industry’s most passionate craftsmen, engineers, businessmen, and aviators while operating profitably, our Synergy kit products will advance only the most proven methods and processes.

Documenting everything necessary to speed the resulting FAA-friendly aircraft through to commercial certification still requires time and a stable process, which is why the positive cashflow and low risk exposure of the kit market supports higher growth toward mass production. Relying on quick-return investors and customer deposits has a very clear business history:  it’s always a mistake.

An aircraft built from a kit can’t be used to make money or fly passengers for hire, but its owners can basically use it with the same and greater freedoms otherwise. However, due to Synergy’s  economy, capabilities, and configurational potential, there is so much money to be made in its commercial applications that even the most aggressive routes to certification receive strong investor advocacy (despite the testimony of aviation’s difficult history.)

Our tested plan navigates this business minefield not just from the start, but from long before there was the enabling breakthrough. Ultra-quality fast-build kit planes are the way to get started, and when the market wants so many of them that low cost and certification of complete airplanes can be an industry-invested result with a reasonable timeline, everybody wins.

Are your performance predictions based on CFD?

No, they flow from classic methods including 2-D flow solvers, spreadsheets, proprietary analysis, and panel codes. The excellent results were highly consistent and are backed by scale model flight test, as well as recent high-end CFD assessments using Large Eddy Simulation. None of the work attempted to validate any active drag reduction measures, just the passive results of natural laminar flow etc. 

Even with recent CFD validations, we prefer to publish actual flight test data at full scale rather than fuel debate over calculations (especially in an ‘open thermodynamic system’!) Just like every ‘active drag reduction’ experiment to come before it,  Synergy challenges the industry’s conventional wisdom regarding preliminary design calculation.  

How can you predict laminar flow over wing and fuselage surfaces?

By analyzing the pressure and velocity distributions required to maintain an attached boundary layer. Natural laminar flow is relatively easy to achieve and quite well established today, although many myths persist. Powered ‘boundary layer control’ makes it even easier to achieve, but the benefits are minimal for the speeds where the most research has been done. Its ideal application is to small airplanes at mid-Mach numbers, not the sailplanes and fighter jets often used for testing the concept.

Pioneering work by August Raspet in the 1960s showed that up to 100% laminar flow is easily achieved at general aviation Reynolds numbers if one is able to use power. Suction, applied to perforated wing skins at a rate of 0.0137 horsepower per square foot of wing area, provided laminar flow on turbulent airfoils and very high maximum lift coefficients, on full scale aircraft.

Like many others, our custom ‘natural laminar flow’ airfoils have a very flat pressure and velocity distribution, easily maintaining laminar flow up to 60% of the wing ‘chord length’. Suction is applied beyond this point, which not only stabilizes the boundary layer, but through our proprietary technology, creates ‘pressure thrust’ to result in extremely low drag. We use a number of commercial grade airfoil analysis codes to compare similar airfoils having flight test data, as well as high-end CFD.

There are several reasons why prior boundary layer control initiatives failed commercially. First, aero research at the time was all about transonic flight and very large airplanes, where it was hard to achieve and not helpful. Second, some aspects, such as contamination, water entry, maintenance, and so forth, require significant effort to address.  Third, dependencies can be created, in a powered lift system, that create both real and imagined safety issues which must be understood, respected, and mitigated. Fourth, airplanes that could use it really weren’t changing, and it didn’t adapt well to old designs. Finally, a push toward blowing, rather than suction, goofed up the ability for designers to capture what they’re really trying to do, in physical terms.

Today, powered BLC is seldom seen as the easy recipe that it is. Much emphasis is given to using specific ‘proven’ details of hole size, pattern, placement, and so on, without insightful consideration of the simple physics of pressure gradient. Thus the attitude: active laminar flow is complicated and expensive. Probably not worth it!!!

Synergy does not require active flow control to achieve its potential, but it does demonstrate its value.

Are there any applications of the Synergy technology for commercial spaceflight?

Definitely. In both Single Stage To Orbit and aerial launch to space, aerodynamic drag is a major design factor. To focus briefly on the comparative relevance of Synergy toward the WhiteKnight/SpaceShip One model, it can be seen that a successful mothership vehicle requires attention to low induced drag, high strength, light weight, and high payload capacity. Uncomplicated twin fuselage design is also helpful.

For the reentry vehicle, favorable wave drag and transonic behaviors; short, strong wings; and control under high-alpha deep stall conditions are required.

In all of these respects, Synergy introduces new and useful solutions. High span efficiency and greatly reduced fuel requirements allow designers to imagine much higher achievables than allowed by prior technology.

Should lower advance ratios or stators be used to straighten unwanted swirl of the propwash for greater thrust?

No. The presumption of inherent loss due to swirl is an artifact of early math. Fluids swirl. The objective of Synergy propulsion is minimum enthalpy mass flow. For wake props in particular,  an unimpeded, lightly swirling propwash displaces a tapering column of airflow efficiently downstream of the aircraft. 

Along the same lines, counter-rotating props are frequently suggested, and we likewise find against it. The best reason to accept the noise, weight, complexity, liability, and inefficiency of counter-rotating props is to mitigate the extreme torque of a high-horsepower, tractor-mounted piston engine. Synergy is a very effective way to counter torque: elegantly.

Can you demonstrate your claimed performance without using a value of e over unity?

Yes. None of our performance claims depend upon having Oswald efficiency greater than one. Flight simulation has typically employed a highly conservative Oswald e = 0.985. Our actual true span efficency is, like many real aircraft with optimal loading and nonplanar wings , much higher than 1. Kroo, in reference 5, summarizes wake-based studies confirming values of e reaching all the way to Prandtl’s theoretical limit of 1.47 for a wide range of nonplanar forms. Though often confused with span efficiency, and (incorrectly) used interchangeably, Oswald efficiency is based upon the teaching that elliptical loading is the only ideal, whereas for nonplanar configurations this assumption is false.

What proportionality constant K are you using?

Defined on the basis of span efficiency and aspect ratio, K = .0307. K reaches similar values using either e = 1.46 or AReq = (bs + .45bh + .45be )/ Cavgwith e set to unity.

What values are you using for minimum drag coefficient of your surfaces?

At cruise Reynolds numbers, without active BLC or propulsive influence, X-Foil and other 2-D analysis codes yield fuselage Cd = .0026, wing Cd = .0026-.0036, and stabilizer Cd = .0045. Since these values reflect natural laminar flow beyond 62% of chord, expected Cd for the 100% laminar flow condition is actually less than the conservative .0020 polar minimum used to calculate our suction BLC condition. Confirmed values of .0008 to .0014 have been demonstrated experimentally by Pfenninger and others.

Preliminary calculation of an aircraft is where many designs go wildly astray. There is an explicit assumption buried in the equations used since the first decade of the 20th century, and for many conditions in the domain where viscosity and inertia are equally implicated in the creation of drag (small aircraft at Mach 0.3 to 0.5), this assumption has been shown to be totally invalid. In the case of Synergy, however, experimental and 3-D CFD testing have revealed that using this conventional approach was conservative. 16

How good are you saying this technology is? Bottom line.

Synergy clearly promises the largest practical fuel economy breakthrough in history. Its architecture correctly and intelligently integrates many proven technologies, each having a huge impact on power requirements and fuel consumption. The design supplies strength, safety, and manufacturing economy without complexity; while eliminating trim drag and cooling drag.

Now that a full suite of assumption-free, power-on tests have been concluded using the most powerful fluid dynamics software on the planet, it is clear that we nailed it. Real-world atmospheric flight testing using large, subscale UAV versions (that amplify undesirable traits) further eliminate surprises. However, this level of clarity is not available to a room full of outside experts, nor typical students of classical aerodynamics.

As reviewer George C. Greene put it (FAA Chief Research Scientist; NASA Langley, retired), “the thing that makes it so hard for me, and probably for others, is the synergy. You are doing so many things (well) at the same time that you have to look at all of them (together). And when you talk about synergy, as you know, they don’t add in a linear way as most classical aero stuff assumes… I don’t think I could put the pieces together the way you did – that is true insight.”

16

Have any peer-reviewed studies been published yet?

Not yet.  Synergy designer John McGinnis is a Senior Member of the AIAA. Several technical papers are in the works for publication after full scale flight test.

These principally concern novel and proprietary aspects of integrated propulsion that are not yet public, such as suction details and wakefan design. The  ‘will-it-fly-well’ aspects have been well established in the conventional manner and are taught in the published and pending patents. Dynamically scaled (unmodified v.18 full scale geometry) electric models have been flying under appropriate low power loading for several years, and extensive CFD work has been carried out.

Long before Synergy’s first public unveiling, more than a dozen respected aeronautical authorities received an early look at Prime versions 18-23 under formal confidentiality agreement. Their opinions, while not purchased for publication, were overwhelmingly positive.

First reactions varied initially, as nearly all failed to grasp that Synergy was not  ‘another box wing,’ nor that there might be hidden symbiotic benefits to discover, such as the absence of interference drag. However, upon more thorough review of the design details and relevant studies in the literature, all but one eagerly agreed that the premise and its execution have significant merit. No one raised any issues not already considered, and the informed consensus was that the work will succeed and will speak for itself.

Since our unveiling, popular acclaim has been universal and criticism highly polarized, mostly because so little can be evaluated without pursuing the matter in great depth. Negativity requires neither effort nor understanding, and is fueled by the same human factors that block progress in all technical endeavors.

Synergy was named Most Innovative new aircraft design by Sport Aviation magazine and the Experimental Aircraft Association in 2011. NASA researchers and others modeled up related designs and validated their own ’10x efficiency’ premise in 2012. Popular Science Magazine, after a months-long review, named it to lead the Best Inventions of 2013.

Extreme interest is continually expressed for getting the full scale (v.32) prototype airborne! Most engineers can’t add anything to the body of research we have obtained to date without it.

Can it be a jet?

Yes, although a better choice would be a small, multiblade turboprop or unducted turbofan, in terms of efficiency and in keeping with the quiet advantages of the concept. Other engines are also possible, but the configuration is not highly suitable for use with air-cooled engines. This intentional bias may help advance the use of liquid cooling in aircraft.

Originally, John intended it to be electric powered, which is how every detail came to be scrutinized and the aerodynamic breakthrough occurred. High torque electric motors, whether pure electric or hybrid, are the preferred eventual powerplant for Synergy designs. Hybrids provide the unique opportunity to lower the risks associated with the use of low-cost, high-volume automotive engines.

With regard to jet propulsion, Synergy supports a host of new technologies that will allow the advantages of a jet without many of their drawbacks. Old ‘reaction thrust’ jets are obsolete.

What is the projected price and availability for the kit?

No kits will be offered until they are real, and that will take a long time and a lot of money. The answers are driven by things that happen after a presumably successful flight test regimen, followed by capitalization, production development, and production flight test.

It is rare to have the opportunity to influence such things fundamentally and at the ‘systems’ level. So, given that we know how much it costs to build similar aircraft using less efficient methods, we can confidently predict that it will be possible for Synergy to substantially lower the cost of market entry. However, it won’t start off that way, given the demand and Synergy’s expected capabilities. Still, early adopters will find the price highly attractive and competitive, and costs will drop when production hits its stride. Our goal is always to offer unmatchable value.

What are the basic airframe and performance specs? Weight, air speeds, engine power, etc?

Synergy has an empty weight of 1650 lbs, 200HP, and 156 sq ft of wing area on a 32 foot wingspan. Casual use of these numbers would be misleading, however, because of our high span efficiency, laminar flow fuselage, and powered lift / powered drag reduction system.

Synergy will offer high performance at both ends of the speed spectrum, but specifications won’t be used for marketing purposes until they have been demonstrated in full scale atmospheric flight testing. More details are found on the technical info page, and with formal non-disclosure agreements we can share more detailed information with prospective partners and collaborators.

A video explaining the basic principles at work in the design is found here: http://youtu.be/UdUNcByJ5eM

Do you have any plans to offer a smaller, two place version? The five place is impressive, but size and power required would drive the price out of most people's range. Most of the pilots I fly with never carry more that two passengers anyhow.

The size and shape of the fuselage is fundamental to its aerodynamic opportunity at the speeds targeted, thus a smaller Synergy is a different bird altogether unless made to fly even faster. Bear in mind, Synergy with one or two seats filled will easily outperform most two seat aircraft on the same or less horsepower. It’s also smaller than a 172 in terms of hangar footprint (L,W,H) even though it can seat six without anyone touching anyone else (!)

Our Deltahawk diesel engine has already shown a 4 GPH cruise in the Velocity aircraft at 146 kts. We can do better than that. At the high end (12GPH), well, we’re not saying.

Build it as a one seater with a pickup bed in back, if you want.

Can there be more than one pilot? I think people would feel safer if there was side-by-side seating.

Yes!

Actually there are already THREE places where we can fly the airplane from, and all of them have a fabulous view.

There is side by side pilot-copilot seating, with a choice of control configuration, right behind the front seat. The left seat is usually where the pilot in command will  choose to sit, when there is more than one person aboard. “Solo” can only be flown from up front, but “dual” can be flown side-by-side OR tandem.

You can also have one instructor with two students, or a VIP passenger up front. (It’s hard to tell the first side-by-side seats are pilot locations in some pictures because the back instrument pylon isn’t visible yet and the controls attach to the wing center section, still being built.) Some people will prefer two seats up front instead of one; it’s an option.

JB

Synergy offers side by side and tandem pilot seating. Solo is flown from front seat only, but passengers can sit there too.

There’s a fourth pilot already, as well. Our autopilot has an emergency auto-approach to landing interface using technologies to safely and automatically put the airplane on the safest available runway by simply engaging the autopilot system (literally, pushing the big red button). Many new features along these lines are already in the market or shortly available to help power the semi autonomous smartplane revolution.

If landing isn’t looking too good for some reason, a pull of the “big red handle” will deploy the ballistic airframe parachute, a very proven technology.

Many other safety features are designed right into this aircraft from the conceptual level onward, including energy absorption, stall resistance, and outstanding low speed handling. The latter two involve a most remarkable, patented ability to avoid stalls and spins, the number one cause of GA accidents. Should one insist on having that capability, Synergy further offers a patented ability to recover instantly from a fully stalled flight condition. You can read more on this feature here.

How fast will it go? How high?

Although it reaches unprecedented speed on only 200 HP, let’s just say that Synergy is faster than we need to assert at this time.

For safety reasons, our service ceiling is 25,000 ft, but in simulation we’ve flown far higher. Our ‘low induced drag’ advantage especially shines at high altitude, yet our ‘active drag reduction’ means you don’t have to climb high just to go fast or gain economy.

What about wing interference drag?

Interference drag occurs when the interaction between objects moving through a three dimensional volume creates unfavorable pressure and velocity distributions, resulting in turbulence. The amount of turbulence that can be created at intersections between wing and fuselage, and wing and winglet, for example, can be surprisingly high. Knowledgeable reviewers of the Synergy conceptual design (shown in early work without a wing fillet) are therefore quick to point this out.

However, shaping these elements is a critical design task. Rather than blindly implement the usual wisdom, which oversimplifies, we strive to work the problem parametrically in 3-D. This approach eventually yields a superior result, without compromising wing placement, or detracting from the propulsive potential of the fuselage in pressure thrust. Due to a nearly ideal volumetric displacement and laminar flow, we also have a more tolerant condition than meets the eye.

Early on, wing-fuselage interference was intended to be captured for cooling. Later optimizations allowed a cooling thrust design, so a preliminary fillet was designed around high-recovery pressure thrust attributes. This feature will be highly refined for the final product.

With continuity of higher pressures on one side of the airfoils and continuity of low pressures on the other, Synergy doesn’t create the kind of conditions that cause ‘interference drag’ (which is really just a catch-all term for unanticipated turbulence.) The intersection of our airfoils is also optimized to provide minimal shed vortices, which is likewise a symptom of discontinuity. Our approach goes beyond a blended winglet design in favor of a temporally optimized volumetric displacement, a true 4-D solution.

What is the primary breakthrough here?

There is a LOT going on in this counterintuitive design, but the obvious thing is also what makes it simple:

Synergy’s patented double boxtail configuration (DBT), which is responsible for the following unique improvements, serves as a catalyst for the simultaneous, low cost adoption of several proven but underutilized drag-reducing technologies, such as laminar flow, wake propulsion, pressure thrust, and boundary layer control. Taken together, these technologies improve aerodynamic performance to the Gabrielli-von Karman limit, which is a benchmark anywhere from two to fifteen times as efficient as typical powered aircraft, depending on their speed. No manned airplane has ever come remotely close to such fuel-efficient high performance in this speed and weight category. Here are some of the benefits of the unique new DBT technology, as it applies to this aircraft in particular.

  1. The  Synergy configuration lowers induced drag (the drag due to lift) to the theoretical limit for a given wingspan. Its ‘non-planar’ span efficiency is 1.46 times that of an optimally loaded planar wing of the same span, allowing a strong, compact form more capable of higher speeds than a long, glider-style wing. Decreasing the induced drag of an airplane provides benefits in climb, at lower speeds, when racing or maneuvering, at higher weights, and at higher altitudes.
  2. The Synergy configuration eliminates complexity. Its simple, seamless wings need no control surfaces or the many parts that would impose; for example, to achieve the major benefits of a sealed gap. Instead, only two moving surfaces are needed to provide a majority of flight control, and these two ‘high aspect ratio elevons‘ are equally simple, one-piece airfoils; merely supported at both ends so they can be rotated for control. (Thanks to its natural turn coordination, Synergy’s twin, V-tail-mounted rudders are rarely required in flight, but yes, we have (two) rudders on the full size aircraft!) Reduced complexity translates directly into reduced weight and reduced cost.
    The scale model doesn't even have rudders. Two simple surfaces provide fully coordinated turn control.

    The 25% scale model doesn’t even have rudders. Two simple tail surfaces provide the outstanding, naturally coordinated turn control seen in our flight test videos.

  3. The weight distribution of the structure is inherently ideal for keeping the structural costs down and the balance right. When flown solo and light, from the front seat, the balance provides nimble handling. As the aircraft gains more people or payload, it remains in proper balance and increases in stability. At maximum weights all remaining payload is carried right on the CG itself, and the aircraft achieves its most stable configuration. (Many airplanes suffer from the exact opposite condition as they get heavier: less stable, less safe.)
  4. Laminar flow and high span efficiency allows a bigger, stronger wing in comparison to typical high-performance designs. Providing increased fuel storage and slower landings, the wings can be stronger and stiffer for a given span loading. Wingtip twist, associated with swept wings, is balanced out of the system under G-loading by an always-proportionate, opposing downforce from the tails. Note, however, that Synergy doesn’t really have any ‘wingtips’. (How many do you see on other aircraft, counting every lift-producing surface?  Each one is a drag source.)
  5. The DBT configuration creates a (patented) novel method for the prevention of stall, and many DBT aircraft exhibit pre-stall behavior similar to the canard configuration. Synergy itself uses a conventional method, in that its controls provide full authority without creating excessive wing angle of attack. In testing, with controls set to allow excessive authority, recovery from intentional stalls was instantaneous and without altitude loss,  due to the large elevons becoming additional flap-like wing area (and, wing airflow control devices !) when commanded to lower the nose. Several versions of Synergy also show promising control behaviors during intentional ‘deep stall descent’ at relatively low speeds. Total control of flightpath and attitude during fully stalled flight, with instantaneous normal flight recovery on command, has been demonstrated in a range of conditions. Certification of such potential requires that every possible combination of conditions be tested. We will not be configuring to allow intentional stalls or deep stall control potential until it has been exhaustively refined in full scale flight test.
  6. The volume of air that is progressively displaced by Synergy in flight changes smoothly along its length in a way that properly matches an optimum ‘body of revolution’ shape in its speed range. This objective, called ‘subsonic area ruling‘, is quite different in character than for supersonic aircraft. Its shape is different and designed to promote stable near-field pressure gradients in all phases of flight, drastically reducing the true source of catch-all “interference drag” and turbulence. It takes an extraordinary aircraft to benefit from, or preserve, refinements in this category. Normally the esoteric benefits of pressure field tailoring at subsonic airspeeds are lost before they can be seen, let alone studied, because of high turbulence in the fuselage region. Thus, conventional wisdom ignores subsonic volumetric tailoring entirely. (Nature, however, doesn’t, and this is part of the reason we can often accurately associate efficiency with beauty.)
  7. The Synergy DBT configuration exhibits superior handling at all speeds, including ideal turn coordination. Most aircraft require a vertical tail and/or rudder input to counter adverse yaw. Synergy carves turns like a finely tuned motorcycle.
  8. The DBT configuration creates a smoother ride in turbulence, and a noticeably more stable platform overall, thanks to moderate wing sweep and effective ‘decalage.’ Synergy’s remarkable stability provides the opposite of a ‘short-coupled’ aircraft. Like a strong man with his hands and feet wedged into the corners of a doorway, Synergy intentionally leverages against the atmosphere with every flight surface, despite having a wing planform that doesn’t, technically, even require tails. (!)
  9. Synergy’s double boxtail configuration creates constructive, beneficial wing-tail interaction, rather than (destructive) “biplane interference”, allowing wing and tail to cooperate together for lower drag. In addition, all airfoil surfaces continue the low pressure or high pressure assignment of the surface  adjacent to it, virtually eliminating the famous interference drag problem common to box wing designs.
  10.  Pilots and passengers  can see in every direction, and the jet-like nose allows all kinds of doors and nose openings to be used for passengers, cargo, and medical access purposes.

Various DBT models have been making the above obvious for some time. Wanna see it fly?

Presently, Synergy Prime, Synergy derivatives, and other DBT aircraft designs are being developed and studied by governments, industry, hobbyists, and academia alike. A large, fast aircraft is required to achieve the size/speed regime where our equally valuable high speed drag reduction technologies make on-demand regional transportation possible, but it’s truly exciting that these many benefits typically result in beautiful, well-mannered aircraft that are a joy to fly.